SCIENCE PRIMERS. [§ i. 



cold, you say it has been dead some time ; if it is 

 still warm, you say it is only just dead— perhaps 

 hardly dead, and may yet revive. 



4. You are warm, and you move about of 

 yourself. You are able to move because 

 you are warm ; you are warm in order that 

 you may move. How does this come about ? 

 Just think for a moment of something which is not an 

 animal, but which is warm and moves about, which 

 only moves when it is warm, and which is wann 

 in order that it may move. 1 mean a locomotive 

 steam-engine. What makes the engine move? The 

 burning coke or coal, whose heat turns the water 

 into steam, and so works the piston, while at the 

 same time the whole engine becomes warm. You 

 know that for the engine to do so much work, to run 

 so many miles, so much coal must be burnt; to 

 keep it working it must be " stoked " with fresh 

 coal, and. all the while it is working it is warm : 

 when its stock of coal is burnt out it stops, and, like 

 a dead animal, grows cold. 



Well, your body too, just like the steam-engine, 

 moves about and is warm, because a fire is always 

 burning in your body. That fire, like the furnace of 

 the engine, needs fresh fuel from time to time, only 

 your fuel is not coal, but food. In three points 

 your body differs from the steam-engine. In the 

 first place, you do not use your fire to change water 

 into steam, but in quite a different way, as we 

 shall see further on. Secondly^ your fire is a burning 

 not of dry coal, but of wet food, a burning which 

 although an oxidation (Chemistry Primer, Ait. 5) takes 

 place in the midst of water^ and goes on without any 



